Ongoing AMOC and related sea-level and temperature changes after achieving the Paris targets

Abstract

While the Atlantic Meridional Overturning Circulation (AMOC) is expected to weaken under increasing GHGs, it is unclear how it would respond to stabilization of global warming of 1.5 or 2.0 °C, the Paris Agreement temperature targets, or 3.0 °C, the expected warming by 2100 under current emission reduction policies. On the basis of stabilized warming simulations with two Earth System Models, we find that, after temperature stabilization, the AMOC declines for 5–10 years followed by a 150-year recovery to a level that is approximately independent of the considered stabilization scenario. The AMOC recovery has important implications for North Atlantic steric sea-level rise, which by 2600 is simulated to be 25–31% less than the global mean, and for North Atlantic surface temperatures, which continue to increase despite global mean surface temperature stabilization. These results show that substantial ongoing climate trends are likely to occur after global mean temperature has stabilized.

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Fig. 1: GSAT and AMOC in stabilized warming simulations.
Fig. 2: Global and North Atlantic sea level.
Fig. 3: Ongoing changes in North Atlantic surface temperature after emissions cessation.
Fig. 4: Upper ocean salinity and density.
Fig. 5: GSAT and AMOC in ZECMIP simulations.

Data availability

Python scripts to create the figures are available at https://gitlab.com/michael.sigmond/amoc_stab. The CanESM2 transient warming simulations are freely available at http://open.canada.ca/data/en/dataset/aa7b6823-fd1e-49ff-a6fb-68076a4a477c. All ZECMIP simulations that were branched off at the point that the diagnosed emissions reached 1,000 PgC are freely available on the portal of the Earth System Grid Federation. Data from the other simulations are available upon request.

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Acknowledgements

We thank Duo Yang for performing the CanESM5 simulations, Yanjun Jiao for technical assistance, and Bill Merryfield and Vivek Arora for their helpful comments on an earlier draft.

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Contributions

M.S., J.F and N.S. conceived the project. M.S. designed the CanESM2 experiments, performed most of the analysis and wrote the manuscript. J.F. and N.S. helped with the analysis and the writing of the manuscript. O.S. proposed and performed the sea-level analysis, helped develop the theoretical framework of the AMOC recovery and helped with writing the manuscript.

Corresponding author

Correspondence to Michael Sigmond.

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The authors declare no competing interests.

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Peer review information Nature Climate Change thanks Andreas Schmittner and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Sigmond, M., Fyfe, J.C., Saenko, O.A. et al. Ongoing AMOC and related sea-level and temperature changes after achieving the Paris targets. Nat. Clim. Chang. 10, 672–677 (2020). https://doi.org/10.1038/s41558-020-0786-0

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